Oral poliovirus vaccine (OPV) can rapidly lose potency when not maintained in a frozen state. Stabilization of OPV to less stringent storage conditions would greatly facilitate the poliovirus immunization program. Some vaccines can be lyophilized and stored in a solid state, but poliovirus infectivity is greatly diminished after lyophilization. We have systematically evaluated different conditions and additives in search of a procedure that would allow the successful lyophilization of poliovirus. Lyophilized material was assayed by both the Elisa assay for D antigen and for infectious virus by a plaque assay. Dramative improvements in viral survival were obtained with the use of a lipid based reagent, which increased viral survival by 1000 and resulted in 20-40% of the viral infectivity surviving lyophilization. Attempts are continuing to further increase virus stability to lyophilization and to evaluate the temporal and temperature stability of the lyophilized virus.